1. Field of the Invention
The present invention relates to a device which generates a target related to an external force to be applied to a legged mobile robot while causing the robot to implement a motion.
2. Description of the Related Art
As a technique for controlling a motion of a legged mobile robot (hereinafter referred to simply as a robot in some cases), there has conventionally been known a technique disclosed in, for example, Japanese Patent Publication No. 4246638 proposed by the applicant of the present application.
With this technique, a state amount related to a posture of the robot (for example, a posture of an upper body of the robot) is sequentially observed while the robot is in motion in order to prevent the posture of the robot from becoming unstable due to, for example, a difference between a floor configuration assumed in a desired motion of the robot and an actual floor configuration, or the like.
In addition, an added floor reaction force (a floor reaction force to be added to a basic floor reaction force in order to attain a desired motion) to be applied to the robot is determined as a feedback manipulated variable for approximating a difference between an observed value of the state amount and a desired value of the state amount as defined by the desired motion of the robot to zero.
Furthermore, by controlling an actual motion of the robot and a floor reaction force actually applied to the robot so as to respectively follow a desired motion of the robot and a desired floor reaction force to which the added floor reaction force has been added, a smooth motion of the robot is achieved.
To cause the robot to perform a variety of jobs, there are cases where it is required to cause the robot to perform a predetermined motion while maintaining a plurality of portions of the robot in contact with a plurality of surfaces to be contacted existing outside the robot (e.g., maintaining the distal end of a leg and the distal end of an arm of the robot in contact with a floor surface and a wall surface, respectively), rather than simply causing the robot to travel on a floor.
In this case, unlike the case where the robot simply travels on a floor, external forces act on a plurality of portions of the robot from the plurality of surfaces to be contacted in an outside world of the robot.
Therefore, in such a case, in order to cause the robot to properly implement a motion, it is necessary to appropriately set targets (such as a desired external force and a desired position of an action point of the external force) related to external forces to be respectively applied from the plurality of surfaces to be contacted, and control the motion of the robot so that external forces that are respectively applied to the robot from the plurality of surfaces to be contacted follow desired external forces while having the actual motion of the robot follow a desired motion. In this case, targets related to external forces are desirably set while adjusting an actual value (observed value) of a predetermined motional state amount of the robot so as to suppress the actual value from deviating from a desired value of the predetermined motional state amount.
However, when external forces are respectively applied to the robot from the plurality of surfaces to be contacted as described above, unlike a case where a floor reaction force is the only external force applied to the robot, how to adjust the external forces respectively applied to the robot from the plurality of surfaces to be contacted becomes a problem if the actual value (observed value) of a predetermined motional state amount of the robot deviates from the desired value of the predetermined motional state amount.
Hence, when generating a desired gait of the robot in the situation where external forces act on the robot from a plurality of surfaces to be contacted, it is essential to adopt a guideline that makes it possible to determine proper targets for the external forces to be applied to the robot from the plurality of surfaces to be contacted.
Hitherto, however, sufficient technological studies have not been carried out with respect to a guideline for setting targets related to the external forces to be applied to the robot from the plurality of surfaces to be contacted while causing the robot to implement a motion in a situation where external forces act on the robot from a plurality of surfaces to be contacted as described above. Accordingly, there has been a demand for establishing a technique that makes it possible to properly generate targets (such as a desired external force and a desired position of an action point of the external force) related to the external forces to be applied to the robot from the plurality of surfaces to be contacted in such a situation.